**1. Introduction**

150 Biogas

The small consumer's individual daily behavior is not known exactly; only an aggregation of all consumers can be calculated. This is due to the fact that consumption values are normally read and collected once a year. For computing purposes a yearly value has to be deduced to a daily or even hourly value by standard load profiles which have implicit uncertainties, of course. One day this shortcoming will be overcome stepwise when Smart

Many measurements which are useful from the technical or simulation point of view may not be useful for economic reasons. Additional measurements cost extra money: equipment, erection, survey and maintenance, etc. So, in fact any computation will have to cope with

Introduction and use of quality parameter tracking systems (for calorific value) require an individual technical acceptance procedure from the Technical Board and a special operating permit. The required accuracy of the computed result must be better than ± 2% in the network area or ± 0.8% from total measuring range. In addition, a number of permanently recorded control measurements are requested to prove the correctness and integrity of the

Calorific value tracking is a most useful simulation tool in order to derive detailed information all over the network for every node and not only at distinct points. This method replaces many costly measurements in the network. Applying historical data to this tool helps to reconstruct all gas parameters and physical states of the past. Using the forwardlooking method it enables even optimization of the gas conditioning for all biogas injections into the network. Aside from existing limitations the precision of the computed calorific value is high. Based on these data billing can be made fair as each consumer could get to

[2] Hass, P.; Röttger, S.; Gasqualitätsberechnung in vermaschten Endverteilnetzen, gwf

[3] PTB, Technische Richtlinie G14, Einspeisungen von Biogas in das Erdgasnetz, 11/2007. [4] Wernekinck, U. et al., Ermittlung des Brennwertes von Erdgasen – Gasmessung und

[5] Schley,P.; Schenk, J.; Hielscher, A.; Brennwertverfolgung in Verteilnetzen, gwf

less data points and less accuracy than desired or theoretically possible.

**8.2 Consumer behavior and data acquisition cycles** 

Metering will be widely introduced and used.

**8.4 Technical board acceptance procedure** 

used data for the Technical Board authority.

know his energy consumption the best way possible.

[1] Cerbe, G.; Grundlagen der Gastechnik, Hanser 2004

Gas/Ergas 9-2009, p. 512 , Oldenbourg Verlag

Abrechnung, 4. Aufl. Vulkan Verlag Essen 2009.

Gas/Erdgas, 9/2011, p. 553-556, Oldenbourg Verlag. [6] STANET User Manual, Fischer-Uhrig Engineering, Berlin 2011.

**9. Conclusion, benefits** 

**10. References**

**8.3 Accuracy, cost-efficiency** 

The pollution of water, air and soil by municipal, industrial and agricultural wastes is a major concern of public autorithies who imperatively have to encourage the development of effective and non expensive treatment technologies. Although it is not recent, the process based on the anaerobic digestion (bio-methanisation) for the treatment of the waste organic fraction, is getting very attractive from the environmental and the economical points of view. It consists of a biological degradation of the organic matter, under anaerobic conditions, where a biogas, mainly methane (CH4) is evolved, and hence providing a renewable source of energy which may be used in the production of electricity and heat.

Generally various types of residual sludges and solid wastes are generated by human activities. They are composed of organic matter which may or may not be easily biodegradeable, inorganic matter, inert soluble and non soluble matter, toxic matter, etc. In order to treat these solid wastes, it is first required to characterise them and second to choose a treatment mode depending on their types and their possible final destinations. According to the physical state, one may distinguish solid wastes (dehydrated sludges, domestic wastes, etc.), liquid wastes (effluents from food, fresh liquid sludges, etc.) and suspensions (sludges from water treatment plant). Classification in terms of the sources may be as follows:


Production of Biogas from Sludge Waste and Organic Fraction of Municipal Solid Waste 153

use organic pollution (biodegradable organic matter) as substrate to produce biogas which can be exploited according to several forms. Thus, anaerobic digestion allows a reduction of the dry matter from approximately 50% (OTV, 1997) and the production of a biogas, mainly methane (55-70%) and carbon dioxide (25-40%), with traces of hydrogen and of H2S, (Mata-Alvares, 2003). Methane can be developed in the form of energy (boiler producing of heat or electricity). At the same time the anaerobic micro-organisms consume little energy, which involves a limited production of muds limited (3 to 20 times lower than an aerobic treatment), (Bitton, 1994). Indeed, the micro-organisms use only approximately 10 to 15 % of the energy of the substrate for their growth (Trably, 2002 and Moletta, 1993), the remaining being used for the production of biogas. Finally, anaerobic digestion allows a reduction of

Anaerobic digestion consists of sludge fermentation, under strict anaerobic conditions. It is made up of four stages: hydrolysis, acidogenesis, acetogenesis and the methanogenesis. To achieve an anaerobic digestion, it is necessary that the reaction kinetics for the consumed or produced component is balanced. The general diagram of anaerobic digestion is presented

*Hydrolyse*

*Acidogene*

*Acetogene*

*Methanogene*

And

**Organic matter Charbohydrates, Proteins, Lipids…**

> *Micro-organisms Hydrolytic and fermentaires*

> > **Alcohols Organic acids Except Acetate**

4% 20%

76%

**H2, CO2 Acetate**

*Acetogene*

28% *Methanogene* 72%

*Hydrogenotrophe S Acetotrophe*

24% 52%

**CH4, CO2** 

Fig. 1. Diagram of trophic chain of the methanogene and its various stages (Edeline, 1997)

the pathogenic micro-organisms.

on Figure 1 (Edeline, 1997)**.**

mineralised organic matter. The sludge characterisation is essential for the choice of the most adequate treatment method as well as for the prediction of each treatment stage performance. Generally distinction is made between primary sludges which are recovered by simple waste waters decantation, and are of high concentrations in mineral and organic matter, and the biological or secondary sludges resulting from a biological treatment of waters. These latter have different compositions, depending on the nature of the degraded substrate, the operation load of the biological reactor and the eventual stabilising treatment.

For the treatment of the different pollution types, vvarious techniques and processes of different chemical, biological and physico-chemical natures as well as a coupling of the last two, are developed. The treatment and the final elimination consist of a sequence of unit operations with a great number of possible options among which the best one is to be chosen, taking into account the upstream (nature, characteristics, and waste quantities) and downstream (local possibilities of final eliminations) constraints as well as the cost.

The present study is more concerned by the biodegradable organic solid wastes which are characterised by a high organic matter concentration, recommanding a biological treatment.

One of technologies to carry out the treatment of the organic fraction of this organic waste is anaerobic digestion (bio-methanization, this process is presented with more details in the next sections of this chapter), which consists of a biological degradation in an anaerobic phase of the organic matter into biogas with a high methane percentage. This technology is becoming essential in the reduction of organic waste volume and the production of biogas, a renewable source of energy. It can be used in a variety of ways, with a heating value of approximately 600 -800 Btu/ft and a quality that can be used to generate electricity, used as fuel for a boiler, space heater, for refrigeration equipment, or as a cooking and lighting fuel.
